Non-invasive imaging technologies allow images of the internal structures or features of a patient to be obtained without performing an invasive procedure on the patient. In particular, such non-invasive imaging technologies rely on various physical principles, such as the differential transmission of X-rays through the target volume or the reflection of acoustic waves, to acquire data and to construct images or otherwise represent the observed internal features of the patient.
For example, in computed tomography (CT) and other X-ray based imaging technologies, X-ray radiation passes through a subject of interest, such as a human patient, and a portion of the radiation impacts a detector where the image data is collected. In digital X-ray systems a photodetector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In the images produced by such systems, it may be possible to identify and examine the internal structures and organs within a patient's body. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
In practice, a physician may only be interested in examining a limited portion of the patient's anatomy for the purpose of formulating a diagnosis. In such a circumstance, it may be desirable to minimize or reduce the X-ray exposure of the patient while still providing sufficient information to produce an accurate diagnosis. That is, it is generally desirable to reduce or minimize X-ray exposure of those portions of the patient anatomy not presently of interest, while still obtaining quality images of the anatomic region-of-interest. In many contexts, this may be difficult to effectively achieve as the region-of-interest will often be located at a different fan angle range with respect to the X-ray beam as a function of the view angle as the X-ray source is rotated about the patient.
Conventional approaches to address this issue may involve the use of a bowtie filter or collimator to adapt the intensity of the X-ray beam, such as in response to the apparent patient thickness in the imaging area at a given viewing angle. However, in practice it may be difficult to move a bowtie filter or collimator quickly back and forth in a manner that provides suitable results.